Lower Lake South

Lower Lake South (Gale Island) (DNR ID: 27-0133-02)


MCWD Site ID: LGI01

Sampling Location - GPS Coordinates:  
44.9149N, -93.5667W

Surface Area: 1069 acres

Max. Depth: 77 ft

 

Directions

Site Information

Historical Information

2009 Water Quality Monitoring

2009 Data Summary

Lake Grades

 

 

Image - Map - Lower Lake South


Directions

Lower Lake South (Gale Island) is located near the cities of Tonka Bay and Greenwood. Head west on Minnetonka Blvd toward Maplewood Rd, and turn left to stay on Minnetonka Blvd. Next turn right to stay on Minnetonka Blvd. Public boat launch is on the right.

Site Information

Lower Lake South is on Lake Minnetonka which is a class 2B lake protected for aquatic life and recreation. Water quality information is available beginning in 1974. MCWD staff have been monitoring the site on Lower Lake South on a bi-weekly basis from the time of ice out (April) to the time of fall mixing (mid-October) since 2006. 

Historical Information

See Previous Reports.

2009 Water Quality Monitoring

Monitoring season started in late April and ended in late October.  A YSI multi-probe sonde was used to measure dissolved oxygen (DO), temperature (oC), pH, and specific conductivity (µS/cm) at each meter depth from the water surface to the bottom.  Additionally, water samples were collected within the first two meters of the surface with a 2-meter composite sampling tube. Samples one meter below the thermocline and one meter above the bottom were collected with a Van Doran water sampler. Surface samples were analyzed for total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), where bottom and thermocline samples were analyzed for TP and SRP. Surface concentrations of chlorophyll-a were also analyzed and measurements of Secchi disc depth were recorded. 

2009 Data Summary

2009 Summer Water Quality Summary
Parameters Range Mean TSI Value Lake Grade
Months   June - Sept.   May - Sept.
Secchi Depth (m) 2.9 - 4.1 3.6 42 A
Surface TP (µg/L) 13 - 24 17.8 46 A
Chlorophyll-a (µg/L) 1 - 6 4.1 44 A
    Overall Score 44 A

The following summary refers to Figure 3.29 (a-d).

  • From late April to late July there was an overall decline in Secchi disk depth, and then
    there was a gradual increase in Secchi disk depth from early August to early October.
    Secchi disk depth ranged between 2.9 m and 4.2 m (standard > 1.4 m).
  • Chlorophyll-a concentrations fluctuated between 4 μg/L and 5 μg/L until late July, when
    concentrations declined. By early August, chlorophyll-a concentration was 1 μg/L.
    Chlorophyll-a concentrations increased to 7 μg/L by early October remaining below the
    standard limit (standard < 14 μg/L).
  • Surface TP concentrations were below the standard limit for the season (< 40 μg/L) and
    fluctuated between 9 μg/L and 24 μg/L. Surface SRP were below detection limit (< 0.005
    μg/L) except in early October when concentrations exceeded TP concentrations*. *Early
    October SRP concentrations were greater than TP concentrations which may be due to
    the presence of silica within the sample (email correspondence; RMB, 2008).
  • Both bottom TP and SRP concentrations increased over the season. In late June, bottom
    TP concentrations declined from 349 μg/L to 257 μg/L in August and then increased to
    500 μg/L in early September. Bottom SRP analysis was not performed in late September
    due to inefficient sample volume upon delivery.

 

image_graph_measuredvalues_lowersouth_2009

image_graph_means_lowersouth_2009

 

Lake Grades and Historical Monitoring Summaries

When available, previous reports are linked to applicable year. Additional lake data previous to 2007 may be available in the applicable year's hydrodata report. If you have additional questions or you are looking for specific information please contact MCWD's Water Quality Staff.

Lower Lake South

Water Quality Grades

2009 A

2008

A

2007

B+

2006

B+

2005

A-

2004

A

2003

A

2002

A

2001

A

2000

A-

1999

A-

1998

A-

 

 

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